Generally, as a printing apparatus for printing a bar code and the like on a recording medium (label paper) utilizing an ink ribbon and the like, a thermal printer such as a label printer and a bar code printer is known. The thermal printer comprises a thermal head, wherein a plurality of heat generating elements is arranged in a direction (namely a horizontal scanning direction) orthogonal to a conveyance direction of a label paper.
The thermal head is configured opposite to a platen roller and is used for conveying the label paper fed by a paper roll along a conveyance path and pressing the label paper and the ink ribbon which are clamped between the thermal head and the platen roller; and a drive motor drives the platen roller to rotate so as to convey the label paper and the heat generating elements of the thermal head are enabled to be in contact with the ink ribbon so as to thermally transfer the ink of the ink ribbon to the label paper. The ink ribbon is rolled up around an ink ribbon winding roller while moving along the conveyance path. (See Japanese Unexamined Patent Application Publication No. Hei 10-157244).
However, in the conventional printing apparatus, there is no other way to confirm the number of utilized label paper but by carrying out visual observation on the residual volume of the paper roll. As a result, the utilization amount of the label paper cannot be counted precisely and the charging cannot be carried out correctly if charging corresponding to the utilization amount of the label paper is wanted.